As is known, a split roller bearing of conventional design employs inner and outer rings between which a series of rollers are held in spaced apart relationship by a cage to locate in raceways formed by the rings. The bearing is made to separate into two halves about a diametric plane and each half of the bearing is then composed of semi-circular inner and outer ring components and a semi-circular cage component. Thus compared with roller bearings which are not of the split type, there is an inherent problem in relation to the strength and stiffness of a two part assembly of two semicircular cage halves when compared with the single piece cage used in non-split roller bearings.
Designers of split roller bearings are aware of this problem and in order to provide the necessary stiffness and strength, conventional cage components for split roller bearings are made from die-cast aluminium or from machined aluminium or gun metal. To fasten the cage components together to form a ring it is conventional to employ separate fastening clips or spring plates which again are of metal to provide the necessary stiffness and strength.
When the split roller bearing is dismantled, the cage halves are separated. In a split roller bearing the cage has an additional function of retaining the rollers when the cage and roller assembly is removed from the bearing.
When the outer race is stationary, the roller train, and hence the cage rotates at about 45% of the speed the inner race. At high speeds the rotational forces on the cage become significant. For cages in solid (non-split) bearings, these forces translate into tensile stress in the cage structure, and because the cage stiffness is constant around its circumference, the cage may increase in diameter but will remain circular. Split bearing cages on the other hand are less stiff at the joints than at right angles to the joints and under high speed rotation will tend to move out at the joints with the cage taking on a form where the circular arcs comprising the cage halves are not tangential at the joints. If the movement at the joints is large enough, the distortion of the cage may impede the rotation of the roller train causing the rollers to skid across the races generating heat and premature failure of the bearing, or the cage may run heavily on one of the races also causing heat generation.
The present invention is provided to reduce or eliminate this disadvantage.